Helically wound tubing

ABSTRACT

A locked seam is formed in ducting formed by convoluted metal strip and seam locking adjacent edges of adjacent convolutions, in which one edge is folded to form a pair of inwardly facing channels and the other is folded to form a generally T-shaped flange and the arms of the T-shaped flange are locked within the channels. The seam may be formed by folding the edges of the strip before it is convoluted to provide along one edge an open U-shaped element facing out of the plane of the strip. A complementary flange is formed along the other edge, generally of similar U-shape or L-shape and after the strip is convoluted and the edges are mated the U-shape is deformed to form the seam. Apparatus for forming the seam comprises a mandrel removably mounted on a frame and two pairs of forming means disposed about the mandrel, one pair being fixed in its location relative to the frame and the other pair being movable with the mandrel, whereby the mandrel can be changed without requiring adjustment of the forming means.

United States Patent [191 Trihey 1 Aug. 21, 1973 HELICALLY WOUND TUBING[75] Inventor: John Massey Trihey, Balwyn,

Australia [73] Assignee: Johns-Manville Corp., New York,

[22] Filed: Apr. 7, 1971 [21] Appl. No.: 132,187

Related US. Application Data [62] Division of Ser. No. 865,275, Oct. 10,1969, PauNo.

Primary Examiner Charles W. Lanham Assistant Examiner-R. M. RogersAttorney-Robert M. Krone et a1.

[5 7 ABSTRACT A locked seam is formed in ducting formed by convolutedmetal strip and seam locking adjacent edges of adjacent convolutions, inwhich one edge is folded to form a pair of inwardly facing channels andthe other is folded to form a generally T-shaped flange and the arms ofthe T-shaped flange are locked within the chan nels. The seam may beformed by folding the edges of the strip before it is convoluted toprovide along one edge an open U-shaped element facing out of the planeof the strip. A complementary flange is formed along the other edge,generally of similar U-shape or L-shape and after the strip isconvoluted and the edges are mated the U-shape is deformed to form theseam. Apparatus for forming the seam comprises a mandrel removablymounted on a frame and two pairs of forming means disposed about themandrel, one pair being fixed in its location relative to the frame andthe other pair being movable with the mandrel, whereby the mandrel canbe changed without requiring adjustment of the forming means.

9 Claims, 20 Drawing Figures PAIENIEDMIBZIMS I 3.753.363

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The invention relates to the formation of helically wound locked seamedducting of the general type described in prior U.S. Pat. No. 3,435,852.

2. Prior Art.

The ducting described in our said prior patent has proved mostsatisfactory in use but, by virtue of its construction relativelycomplex machinery has been required to form the locked seam. Apparatusfor the production of the ducting is described in our prior U.S. PatentApplication Ser. No. 638,393 and this apparatus comprises a mandrelhaving a number of forming and driving rollers arranged about itscircumference, which apparatus operates to form the locked seam. Thisrequires very accurate setting of the rollers and a further disadvantageof this construction is that since each mandrel can be used to form onediameter of duct only, to change from one duct size to anothernecessitates the changing of the mandrel and the adjusting the ofpositions of the many forming rollers. In practice therefore we havefound it necessary to change the whole forming head when changing toanew duct size. Furthermore, the construction of the double locked seamaccording to our prior application requires that in the initial stagesof construction, the flange and channel from which the seam is formedhaving a substantially depth and accordingly they are considerablystretched in bending about the mandrel. This creates particular problemsif the material is not sufficiently ductile.

SUMMARY The primary object of this invention is to provide a new form oflocked seam construction which may lead to the simplification of theapparatus necessary for its formation. A further object is to provide amethod of forming'a locked seam in which the major part of the formationof the seam can be carried out on the material in strip form before theedges are brought together. In particular, it is the object to providesuch a method for use in the formation of helically wound ducting inwhich a substantial part of the seam-forming operation can be carriedout before the material is convoluted in the coiling head. The preferredform of the invention allows the formation and closing of the seam to beperformed almost entirely by the use of simple bending and pressingoperations avoiding any substantial drawa ing operation during theprocess. The preferred form of the invention also substantiallyeliminates buckling or wrinkling of the metal at the seam.

According to this invention there is provided a tube formed fromhelically wound ductile strip material with adjacent edges of the stripjoined together by a locked seam wherein said locked seam comprises apair of generally oppositely directed channels formed in one edge anddisposed on opposite sides of the longitudinal medial planeof the seamwith their mouths facing, and a complementary flange of generallyT-shaped cross section formed in the other edge with its arms disposedone within each of the said channels.

According to one form of the inventionthe channels are directly facingone another and the arms of the flange are substantially co-planar. Inanother form of the invention the channels are disposed so that theirdirections of facing intersect at an angle slightly less than 180 andthe arms of the flange are correspondingly angled. In this constructionthe channels are disposed to face slightly outwardly of the tube.

The invention further provides a method of forming helically wound seamlocked tubing from ductile strip material comprising the steps offorming in one edge of the strip at least one element of U-shapedcross-section and in the other edge at least one complementary flange,convoluting the strip and mating the adjacent edges of the convolutionsso that the flange lies within the U-shaped element, folding the or eachU-shaped element and the flange to form a pair of generally oppositelydirected channels and a pair of generally oppositely directed flangearms lying within the channels, and flattening the channels to grip theflange arms within'them and form a locked seam.

A preferred method of forming the seam according to this inventioncomprises the steps of forming in one edge of the strip a U-shapedelement whichis formed with an open mouth directed at rights angles tothe general plane of the strip and outwardly of the formed tube, saidU-shaped element having an outer wall and an inner wall, the inner wallbeing formed by a deep corrugation or rib formed by folding the strip;forming in the other edge of the strip a similar deep corrugation or ribdisplaced from the edge of the strip to leave an edge flange;convoluting the strip, and mating the adjacent edges of the convolutedstrip so that the flange lies within the U-shaped element and the outerwall of said element lies within the rib of the flanged edge of thestrip, and bending the ribs inwardly towards each other to form theU-shaped' element into a pair of inwardly facing channels and the flangein a flange of T-shaped cross-section with the arms of the T lyingwithin the channels and flattening the channels so that the arms of theflange are locked within the channels and the outer wall of the channelis locked within the rib of the flanged edge.

In an alternative form of the invention the locked seam is formed byfirst folding one edge of the strip to form a U-shaped element with anopen mouth directed at right angles to the general plane of the stripand forming a complementary flange element in the other edge mating theedges, inwardly deforming the side walls of the U-shaped element toclose the mouth thereof so that the side walls of the element form withthe web thereof two inwardly facing channels and the flange element isbent over on itself to a T-shaped configuration, and flattening the seamto lock the arms of the flange within the channels. v The inventionprovides a still further method of forming the seam comprising the stepsof first forming in one of the edges of the strip a pair of parallelU-shaped elements arranged-side by side and in the other edge a pair ofparallel flange elements arranged side by side, mating the flangeelements within the U-shaped and spreading the channels apart by bendingthem in opposite directions about the longitudinal medial plane of g theseam so that the U-shaped elements form two in wardly facing channelsand the flange elements are substantially co-planar and form the arms ofa flange of generally T-shaped cross-section with the arms lying withinthe channels, and flattening the channels to lock the arms of the flangewithin the channels.

The invention also provides apparatus for forming .the periphery of themandrel for seaming together adjacent edges of strip material convolutedabout the mandrel characterised in that the forming means comprise twoco-operating pairs of forming means one pair being mounted on the frameand the other pair being mounted so as to be removable on removal of themandrel whereby on substitution of one size of mandrel for another onlyone of the pairs of forming means needs to be adjusted to accomodate thenew mandrel. Preferably the mandrel is a fixed substantially cylindricalmandrel and at least one of the forming means comprises a rotatableroller located in a cavity formed in the mandrel.

The reference above to a flange being formed on one edge of the strip isnot to be understood as limiting the invention to the provision of aplain flanged edge. The expression flange and channel have been usedlargely for convenience of description and as will be apparent from thedescription of the embodiments of the invention the flanged edge of thestrip may be in fact constituted by a channel and be substantiallysimilar to the edge which is referred to as terminating in a channel.

In order that the invention may be better understood the preferredembodiment and a number of alternative constructions will now bedescribed by way of example and with reference to the accompanyingdrawings:

BRIEF DESCRIPTION OF DRAWINGS:

FIG. 1 is a plan view of part of apparatus for forming convolutedcorrugated tubing by the method of this invention;

FIGS. 2 to are cross-sectional views on the lines 2-2, 3-3, 4-4, 5--5respectively of FIG. 1 and illustrate the steps in the formation of thestrip for use according to this invention;

FIG. 6 is a perspective view of a section of strip according to theinvention;

FIG. 7 is a side elevation partly in cross-section of the forming headshown in FIG. 1;

FIG. 8 is an end elevation partly in cross-section of the forming head;I

FIG. 9 is an enlarged cross-sectional view of the forming mandrel(broken away to reduce space);

FIG. 10 is a fragmental cross-sectional view of a modification of theconstruction shown in FIG. 9;

FIG. 11 is a plan view to a small scale of a modification of theapparatus for producing small diameter ducting;

FIG. 12 is a cross-sectional view to a larger scale of the apparatus ofFIG. 11;

FIGS. 13 and 14 are enlarged fragmental views showing the stages in theformation of the seam in the apparatus of FIGS. 11 and 12;

FIG. 15 is a side elevation (from the opposite side to FIG. 7) of theforming head showing the arrangement of the tube spiking mechanism;

FIG. 16 is a cross-sectional view (on an enlarged scale) on the lines 1616 in FIG. 15;

FIG. 17 is a fragmentary cross-sectional view showing a mandrel andforming mechanism for forming the seam by an alternative method;

FIG. 18 shows diagrammatically the stages in the formation of a seam bythe method employing the forming head of FIG. 17;

FIG. 19 shows diagrammatically yet another method of forming the seam ofthis invention; and

FIG. 20 shows diagrammatically how, using the method and apparatus ofthis invention mandrels of different size may readily be substitutedonefor another on the one machine.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIGS. 1 to 5,ductile strip material, such as aluminum, 1 is formed to a corrugatedconfiguration (see FIG. 2) by corrugating rollers (not shown) and in thelast stages of its formation narrow edge ribs 2, 3 are formed by formingrollers 4. The strip then passes to another set of forming rollers 5 andthe ribs 2 and 3 are pushed in by crushing rolls 6, 7 to make the ribsdeeper and narrower.

The strip then passes to the next set of rolls 8 where the edge marginsof the strip are turned down so that channels 11, 12 are formed in eachedge, bounded respectively by downturned edge margins 13 and rib 2 andrib 3 and downturned edge margin 14. At the same time the bases of thechannels are indented by the forms 9, to form convexities 10.

The strip is then perforated by perforating head 15 and is passed overan initial forming roller 16 to the forming head 17 where it isconvoluted about mandrel 18 to form a tube 19.

As the strip is fed to the forming head 17 it passes between formingrolls 21, 22 and is coiled about mandrel 18 to a helical configurationwith the edges of the strip in mating relationship.

For convenience of description the channel 11 will be referred to as achannel element and the channel 12 which is narrower and fits within thechannel 11 will be referred to as a flange. As the strip is coiled aboutthe mandrel with the flange 12 lying in the channel element 1 1 itpasses beneath deforming rollers 23 which deform the ribs 2, 3 inwardlyto partly close the mouth of the channel 11. A small backing roller 20is let into the mandrel below the deforming rollers 23 to reducefriction. As the seam thus partly formed continues around the mandrel itagain passes between the forming rolls 2], 22 at a position where therolls are shaped to complete the inward deformation of the ribs and tocrush the seam flat as shown in FIG. 9.

The final operation of closing the seam forms the flange to a generallyT-shaped configuration with the edge 14 squashed down to form one arm ofthe T and the rib 3 squashed in to form the other arm of the T and withthe shank of the T formed by the portion 3a of the rib 3. The two armsof the T are gripped in the inwardly facing channels formed by bendingover the edge margin 13 and the rib 2, and are held within thesechannels (see FIGS. 9 and 10).

The formation of the seam in the operation described above was carriedout partly by the corrugating rolls and the crushing rolls 6, 7 andthereafter the seam was completed by mating the edges of the strip andbending the ribs 2, 3 by means of the deforming rolls 23 and the formingrolls 21, 22. Thus it will be seen that all of the initial steps in theformation of the seam are carried out before the two edges are broughttogether and that after-mating of the edges, only the steps of bendingin the ribs to form the two oppositely directed channels and pressingthem down, are required to be performed. It will be observed also thatthe double locked seam is formed from channels which are only'half theheight of that which would be necessary for the formation of the doublelocked seam of our prior Application Ser. No. 5,601/66. Thus there issubstantially less stressing of the material in forming it about thecoiling head. Furthermore, in view of the fact that only two operationshave to be performed after the edges of the strip are brought together,these operations can be carried out with only two sets of formingrollers. Thus it is not necessary, as in the prior construction, toprovide a large number of rollers positioned about the circumference ofthe forming mandrel. Because of the very much simpler construction ofthe forming head it becomes a relatively simple matter to substitute oneforming head for another when it is desired to change from one tube sizeto another. This feature of the invention will be more fully describedhereinafter.

The provision of the convexities in the bases of the channels has theeffect of eliminating wrinkling or buckling of the seam when the stripis convoluted about the mandrel. Without the convexity such wrinkling islikely to occur because of the distance of the mass of metal in the baseof the seam from the neutral axis of curvature. The provision of theconvexities reduces this effect. A further advantage derives from thefact that, as is best seen from FIG. 14, the flattening of the seamcauses the ribs to tend to straighten out the convexity and, due to itselasticity, the convexity tends to spring back thereby forming a tighterseam.

A slight modification of the seam above described is shown in FIG. 10 ofthe drawings. In that figure convexities 10 in the channels are notformed and the end portions of the forming rolls 21, 22 are shaped sothat the final seam instead of being crushed flat is slightly bent aboutits longitudinal medial plane. This slight deformation of the seamalters the line of action of forces tending to open the seam andconsequently leads to a somewhat stronger joint.

A further modification of the apparatus is shown in FIGS. 11 to 14. Thismodification is designed primarily for use in the manufacture of smalldiameter pipes say, of the order of 2% to 3 inches diameter. For suchpipes it is not possible to inset the forming roller 21 into the bottomof the mandrel and also because of increased resistance to bending overthe small diameter it is desirable for the deforming rollers 23 to bedriven to help clear the tube from the mandrel. In this modification theforming roll 21 is omitted and the deforming rollers 23 are pleaced by adriven grooved forming roll 23A provided with a V groove 30 to inwardlydeform the ribs 2 and 3. Flattening down of the seam is done by a plainroller 31 provided at the end of the mandrel. As will be seen from FIG.11, the roller 22, the mandrel 18 and the roller 23A are each arrangedwith respect to one another at an angle equal to the helix angle of thetube. The flattening roller 31 is however mounted on an axis parallel tothat of the roller 22 with which it cooperates.

In another modification the mandrel 18 may be rotatable.

FIGS. 15 and 16 show in some more detail the spiking mechanism of theapparatus of this invention. As in the construction shown in ourprevious Application Ser. No. 5,601/66 the spiking mechanism comprises aspiked roller and a backing roller. However, in this case instead ofbeing arranged to spike the strip after the tube is formed, as in thepreferred embodiment shown in our prior application, the mechanism ishere arranged to spike the strip before it is convoluted about themandrel. The backing roller 36 is mounted on the machine frame in frontof the initial forming roller 16 and the spiking roller 37 is mountedabove it on an axle 38 carried by a bracket 39 pivoted on a pivot pin 41of the frame section 42 which carries the backing roller 36. The bracket39 is connected at its upper end to a ram and cylinder mechanism 43which can be operated to pivot the bracket about the pivot 41 andthereby move the spiking roller 37 toward or away from the strip torender it operative or inoperative or to vary the degree of penetrationof the spikes thereby varying the sizes of the holes formed.

FIG. 17 shows a modification of the forming head for forming the seam bythe first of the above-mentioned alternative methods. FIG. 18 shows thesteps in the formation of the seam by this method. In this method thestrip is formed at one edge with a L-shaped flange 51 and in the otheredge with a U-shaped channel element 52 the channel element in this casebeing formed such that its open mouth is inwardly directed with respectto the formed tube. As the strip is fed to the mandrel the L-shapedflange 51 is mated with the channel element 52 and as the strip passesaround the mandrel it passes between nipping-in rollers 53 which nip-inthe base of the channel to partially close its mouth as shown at A inFIG. 18. As the seam passes further around the mandrel it is finallyflattened by the forming rollers 21; 22 as in the previous construction.The steps in the formation of the seam by the second alternative methodare shown diagrammatically in FIG. 19. In this method the edges of thestrip are formed so that in one edge there is a pair of ribs 61, 62which are outwardly directed with respect to the tube and in the otheredge there is a pair of channels 63, 64 formed with their mouths facinginwardly with respect to the tube. As the strip is convoluted about themandrel the ribs 61, 62 are first mated with the channels 63, 64 asshown at A in FIG. 19. The channels are next spread apart as shown at Bin FIG. 19 and finally they are flattened down to form oppositelydirected channels with the arms of the flange 61, 62 locked within themas shown at C in FIG. 19.

It will be seen with the resultant seam formed by either of the methodsof FIGS. 18 and 19 is the same and also that the seam is substantiallythe same as that formed by the method illustrated with reference to FIG.9 of the drawings except that in the latter case the body of the seamlies within the tube whereas in the two former cases the body of theseam lies on the outside of the tube. Also in the construction shown inFIG. 9 each arm of the flange is of double thickness since it is formedfrom an element which is originally channel shaped whereas in theconstructions shown in FIGS. 18 19 the free arm of the flange is ofsingle thickness the flange having been formed from an original L-shapedelement. It would be readily apparent however that the double thicknessportion can easily be omitted from the construction shown in FIG. 9 andlikewise that the freearm of the flange shown in FIGS. 18 and 19 can beof double thickness rather than single thickness.

The seam according to this invention and its method of formation haveenabled us to produce apparatus in which the substitution of one mandrelfor another when a different sized tube is to be produced can be carriedout relatively simply. This is illustrated in FIG. 20 of the drawingswhere illustrations (a), (b) and show medium sized, small sized andlarge sized mandrels respectively which can all be secured to the samebasic forming head 17 in a simple operation. That this can be done isdue to the fact that the formation of the seam is carried out at onlytwo locations about the periphery of the mandrel. At the first locationa pair of forming rollers (such as those shown as 21 and 22 in FIGS. 7and 8) are mounted on the machine frame and are common to all sizes ofmandrel. The forming means at the second location comprise the angleddeforming rollers 23 and the surface of the mandrel itself oralternatively the backing roller (see FIG. 8). The deforming rollers 23are carried on the bracket 70 which is bolted to the mandrel 18 and themandrel 18 itself is secured to the frame 71 of the coiling head bymeans of bolts 72.

It will thus be seen, particularly by reference to FIG. 20, that tochange from one sized mandrel to another all that is necessary is toundo the bolts 72, remove the existing head and substitute a new one.Since the roller 21 is located within the cavity 73 in the mandrel butis not attached to the mandrel it, and its co-operating roller 22, willnot be disturbed by this changeover operation. It is thus possible inthe construction according to this invention to change from one mandrelsize to another merely by changing the mandrel and its associatedforming rollers (such as 23) without the necessity for any adjustment ofthe other forming means 21, 22.

The seam and the method of apparatus for its construction provided bythis invention provides a strong and reliable seam and one which can bemade on appa ratus in which the substitution of one forming head foranother can readily and rapidly be carried out without the complicatedand delicate adjustment of the forming means which was necessary in theconstruction according to our prior Application Ser. No. 5,601/66. Itwill also be seen that according to this invention the major proportionof the seam forming operation is carried out before the strip reachesthe mandrel. The apparatus is accordingly more easily and readilycontrolled and adjusted than was the case in the previous construction.

We have described above a number of alternative methods for theformation of the seam according to this 4 invention and also a number ofmodifications which may be made to the apparatus for the construction ofthe seam. It will be appreciated however that other variations andmodifications could be made to the method and apparatus within the scopeof the invention as defined by the following claims.

I claim:

1. Apparatus for forming helically wound tubing from ductile stripmaterial comprising: a frame, a mandrel mounted on the frame butremovable therefrom,

and forming means located about the periphery of the mandrel for seamingtogether adjacent edges of strip material convoluted about the mandreland characterized in that the forming means comprise two cooperatingpairs of forming means with one pair being mounted on the frame and theother pair being mounted to be removable with the mandrel whereby onsubstitution of a new mandrel of one size for another mandrel the onepair of forming means is compatible with either mandrel and only theother pair of forming means needs to be adjusted to accommodate the newmandrel.

2. Apparatus as claimed in claim 1, wherein said other pair of formingmeans comprises a first forming element constituted by the mandrel, anda second element arranged to co-operate with said first element and saidsecond element being mounted on the mandrel for removal with the manrel.

3. Apparatus as claimed in claim 2, wherein the mandrel is a fixedsubstantially cylindrical mandrel and said one pair of forming meanscomprises a pair of rollers one of which is located in a cavity formedin the mandrel.

4. Apparatus as claimed in claim 1, wherein there is further providedspiking means to spike the strip before the strip is fed to the mandrel.

5. Apparatus as claimed in claim 4, wherein the spiking mechanismcomprises a spiked roller arranged on one side of the strip and abacking roller arranged on the other side of the strip to support thestrip as it is spiked by the spiking roller.

6. Apparatus as claimed in claim 4 wherein the spikes are tapered spikesand means is provided to vary the position of the spiking means relativeto the strip to render it operative or inoperative and to vary thedegree of penetration of the strip by the spikes thereby varying thesize of holes formed by the spikes when the spiking mechanism is in anoperative position.

7. Apparatus as claimed in claim 1 wherein said other pair of formingmeans comprises a first forming element constituted by a roller mountedwithin the mandrel, and a second element arranged to co-operate with thesaid first element and mounted on the mandrel for removal with themandrel.

8. Apparatus as claimed in claim 7, wherein the mandrel is a fixedsubstantially cylindrical mandrel and said one pair of forming meanscomprises a pair of rollers one of which is located in a cavity formedin the mandrel.

9. Apparatus as claimed in claim 1, wherein the mandrel is a fixedsubstantially cylindrical mandrel and said one pair of forming meanscomprises a pair of rollers one of which is located in a cavity formedin the mandrel.

1. Apparatus for forming helically wound tubing from ductile stripmaterial comprising: a frame, a mandrel mounted on the frame butremovable therefrom, and forming means located about the periphery ofthe mandrel for seaming together adjacent edges of strip materialconvoluted about the mandrel and characterized in that the forming meanscomprise two co-operating pairs of forming means with one pair beingmounted on the frame and the other pair being mounted to be removablewith the mandrel whereby on substitution of a new mandrel of one sizefor another mandrel the one pair of forming means is compatible witheither mandrel and only the other pair of forming means needs to beadjusted to accommodate the new mandrel.
 2. Apparatus as claimed inclaim 1, wherein said other pair of forming means comprises a firstforming element constituted by the mandrel, and a second elementarranged to co-operate with said first element and said second elementbeing mounted on the mandrel for removal with the manrel.
 3. Apparatusas claimed in claim 2, wherein the mandrel is a fixed substantiallycylindrical mandrel and said one pair of forming means comprises a pairof rollers one of which is located in a cavity formed in the mandrel. 4.Apparatus as claimed in claim 1, wherein there is further providedspiking means to spike the strip before the strip is fed to the mandrel.5. Apparatus as claimed in claim 4, wherein the spiking mechanismcomprises a spiked roller arranged on one side of the strip and abacking roller arranged on the other side of the strip to support thestrip as it is spiked by the spiking roller.
 6. Apparatus as claimed inclaim 4 wherein the spikes are tapered spikes and means is provided tovary the position of the spiking means relative to the strip to renderit operative or inoperative and to vary the degree of penetration of thestrip by the spikes thereby varying the size of holes formed by thespikes when the spiking mechanism is in an operative position. 7.Apparatus as claimed in claim 1 wherein said other pair of forming meanscomprises a first forming element constituted by a roller mounted withinthe mandrel, and a second element arranged to co-operate with the saidfirst element and mounted on the mandrel for removal with the mandrel.8. Apparatus as claimed in claim 7, wherein the mandrel is a fixedsubstantially cylindrical mandrel and said one pair of forming meanscomprises a pair of rollers one of which is located in a cavity formedin the mandrel.
 9. Apparatus as claimed in claim 1, wherein the mandrelis a fixed substantially cylindrical mandrel and said one pair offorming means comprises a pair of rollers one of which is located in acavity formed in the mandrel.